Simplify the following expression: $r = \dfrac{y^2 + 13y + 36}{y + 4} $
Answer: First factor the polynomial in the numerator. $ y^2 + 13y + 36 = (y + 4)(y + 9) $ So we can rewrite the expression as: $r = \dfrac{(y + 4)(y + 9)}{y + 4} $ We can divide the numerator and denominator by $(y + 4)$ on condition that $y \neq -4$ Therefore $r = y + 9; y \neq -4$